Search for multiple K + L photoionization in solid transition elements by x-ray-absorption spectroscopy

The x-ray absorption of transition metals from Cr to Zn is examined in the energy region of K+L double photoabsorption. A variational procedure is developed to extract correlated components from pairs of spectra. Applied to absorption spectra taken at different sample temperatures, the procedure is used to suppress the extended x-ray-absorption fine-structure oscillations that pervade the K+L region in this range of elements. A relative sensitivity of 2×10$^{−3}$ to 3×10$^{−4}$ of the absorption coefficient, depending on the sample quality, is achieved. No significant features attributable to multiple photoexcitation are found in the spectra on that level, so that previous reports of K+L edges for Co, Ni, and Zn are not confirmed